Then I saw an angel coming down from heaven, holding in his hand the key to the abyss and a huge chain.
References for Revelation 20:1
He seized the dragon, the old snake, who is the devil and Satan, and bound him for a thousand years.
He threw him into the abyss, then locked and sealed it over him. This was to keep him from continuing to deceive the nations until the thousand years were over. After this he must be released for a little while.
Then I saw thrones, and people took their seats on them, and judgment was given in their favor. They were the ones who had been beheaded for their witness to Jesus and God's word, and those who hadn't worshipped the beast or its image, who hadn't received the mark on their forehead or hand. They came to life and ruled with Christ for one thousand years.
References for Revelation 20:4
The rest of the dead didn't come to life until the thousand years were over. This is the first resurrection.
Favored and holy are those who have a share in the first resurrection. The second death has no power over them, but they will be priests of God and of Christ, and will rule with him for one thousand years.